(1) Field of the Invention
The present invention relates to fish sex discrimination equipment and method, and more particularly relates to equipment and a method by which fish sex can be discriminated at high speed and with high accuracy utilizing a difference in degree of a transmission of light emitted between the fish roe of a female fish and the milt of a male fish.
(2) Description of the Related Art
Recently, in Japan, herring roe is of great value as "Kazunoko", however, male fish are of little value. Accordingly, to obtain the herring roe from the female fish, it is preferable that the female fish be separated from the male fish so that the roe can be easily obtained, and the time for working and processing can be reduced. In addition, in European countries people eat male herring pickled in vinegar. Therefore, for this purpose it is efficient that the male and female herrings be separated with only the male herrings being processed.
As a result, completely automatic fish sex discrimination equipment which can discriminate the fish sex at high speed and with high accuracy is desired.
An example of conventional fish sex discrimination equipment is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 51-100495 entitled "Nondestructive Sex Discrimination Method of Fish and Equipment Thereof".
The equipment comprises sex discrimination equipment providing a control unit, a detection unit including a light reception portion, and a light source including a light emitting portion; a hopper in which fish to be discriminated are put, a flusher by which the fish are washed, a duct through which the fish are guided to the sex discrimination equipment, and a sorting unit for separating the male and female fish.
In this equipment, the discrimination of fish utilizes a difference of transmission degree for light energy emitted from female roe and male milt.
In the method and the equipment disclosed in Japanese Unexamined Patent Publication (Kokai) No. 51-100495, or U.S. Pat. No. 3,859,522, entitled "Method for Nondestructive Testing of Fish for Sex", the light energy is illuminated onto a genital gland area of the fish to be discriminated, and if the transmission energy is large, the fish is determined to be a female. That is, a light spot is illuminated on the center of the genital gland area, and the quantity of light transmitted is measured and the discrimination of whether the fish is male or female is carried out.
However, if the light spot is not correctly illuminated on the center of the genital gland area, the thickness of the roe or milt decreases, the light transmission quantity changes, and a stable discrimination cannot be obtained. Particularly, since the genital gland area is narrow in the belly to back direction, if the light spot moves off in the belly to back direction, the stability is considerably reduced.
Accordingly, there arises a problem that the light spot must be set accurately in the center of the genital gland area of the fish so as to obtain a stable discrimination result.
Further, in manual supply type equipment, the fish to be discriminated are trued up on the bucket at the head, tail, back and belly thereof by hand, and put on the bucket to coincide a light transmission hole with the center of the genital gland area, then the fishes are supplied to the sex discrimination equipment.
A spot of light is projected from a light projection unit onto the genital gland of the fish to be discriminated, the spot light arrives at a light reception unit, and whether the fish is male or female is discriminated, when the fish is between the light reception unit and the light projection unit, and when the light transmission hole of a bucket on a bucket conveyor is just above the light projection portion. In this case, information used for the discrimination is spot information depending on the area of the light transmission hole.
To reduce the amount of manual labor, instead of supplying the fish on the bucket manually, the separation of the fish automatically one by one and arrangement in the direction head to tail and back to belly using a machine can be considered, however, the complete arrangement in the directions head to tail and belly to back is difficult, and even though the amount of manual labor is reduced, the discrimination rate sometimes also reduces.
Accordingly, if the fish sex discrimination equipment or method disclosed in Japanese Unexamined Patent Publication (Kokai) No. 51-100495 or U.S. Pat. No. 3,859,522 is utilized, it is necessary that the fish be arranged on the bucket of the bucket conveyor by manual trueing in the direction from head to tail and belly to back, and that the fish be supplied to fit the hole for the light transmission to the center of the genital gland area of the fish to coincide the light spot position with the center of the genital gland area.
For the above reasons, five workers are needed to supply fish at a rate of 300/min. Thus, a first problem in which the reduction of workers is prevented arises. Also, a second problem arises in which the positioning between the hole for the light transmission and the genital gland area is not accurate when done manually, and the discrimination rate reduces.
Further, by using the conventional equipment or method, the light spot being information forming a point must be illuminated on the center of the genital gland area so accuracy in positioning is needed. The accuracy in positioning is somewhat satisfied by manually placing the fish to be discriminated on the predetermined position of the bucket, however, the amount of work for the sex discrimination operation cannot be reduced. This is a third problem. While, for the work quantity reduction, the fish can be trued on a predetermined position by using the automatic supply unit, a completely reliable arrangement is difficult. Thus a fourth problem arises in which the discrimination rate is decreased compared with the manual handling. The present invention was created in consideration of these conventional problems.